Log in
Register
Home
Forums
New posts
Search forums
What's new
Featured content
New posts
New profile posts
Latest activity
News
Members
Current visitors
New profile posts
Search profile posts
Features
Log in
Register
What's new
Search
Search titles only
By:
Search titles only
By:
New posts
Search forums
Menu
Install the app
Install
Reply to thread
Home
Forums
Pro Audio
Varsity
Suspect amp power ratings
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Message
<blockquote data-quote="John Roberts" data-source="post: 99988" data-attributes="member: 126"><p>Re: Suspect amp power ratings</p><p></p><p></p><p>As i think I already mentioned, there is no accepted quantification for duty cycle. Since we entered the age of 2 ohm operation (like 4 ohm bridged) there are no continuous operation amps sold to consumers that I know of. </p><p></p><p>As i think I also mentioned (recently if not in this thread), all clip limiters are not created equal. IIRC and I am not an expert on Crest, but I knew them as a competitor (before PV bought them). Their version of clip limiting used a somewhat slower attack time, that actually delivered a louder signal, with the mostly inaudible leading edge or complete very brief transients passing unmolested and allowed to clip. In my experience consumers always liked louder better, so the Crest variant was successful in the marketplace while not preventing as much clipping as other more conservative clip limiters. </p><p></p><p>Worst clip limiter I ever heard was one Yamaha amp model (no I don't recall which one) we were bench testing, but I wouldn't expect all of them to sound that bad (they couldn't). </p><p></p><p></p><p>When operating at the limits of amplifier current capability (2 ohm) this is not very surprising. Add the variables of loudspeakers that are not pure resistive loads, and some amps with VI (secondary breakdown) limiting protection. This secondary breakdown protection is a variant on current limiting that involves both current and voltage across the power device, so different than simple current limiting. Audible perturbations could occur related to protection circuits tripping when driven hard with marginal loads. Not to mention different duty cycle capability. This may not show up with resistive loads. </p><p></p><p>This is yet another reason I don't advocate routine 2 ohm operation... Spec your system to work well within the capability of the amps (4-8 ohm) and use the extra drive capability to use in emergencies if an amp failure occurs so you can double up a load to finish the gig. If all amps are loaded to the max you have no option to limp along. (Back in the day I've heard anecdotes of finishing shows loaded to 1 ohm but it wasn't pretty.) </p><p></p><p>Customers are attracted to driving amps at 2 ohms since it seems like free power. Nothing in life is free... That said I expect the modern generation class D amps to be somewhat less affected by load impedance (ignoring frequency response interaction with output filters). </p><p></p><p>It is difficult to make listening evaluations of amps driving loudspeakers. One test we tried at Peavey during development of one amp series, was to load up an amp with some PA speakers, in parallel with a second pair of low efficiency studio monitors in a different isolated sound space, so we could drive the amps hard but listen over the studio monitors without hurting ourselves (I still wore plugs). </p><p></p><p>We kind of explored this duty cycle issue (or at least I raised it) back when Bink did his amp shoot-out years ago. </p><p></p><p>JR</p></blockquote><p></p>
[QUOTE="John Roberts, post: 99988, member: 126"] Re: Suspect amp power ratings As i think I already mentioned, there is no accepted quantification for duty cycle. Since we entered the age of 2 ohm operation (like 4 ohm bridged) there are no continuous operation amps sold to consumers that I know of. As i think I also mentioned (recently if not in this thread), all clip limiters are not created equal. IIRC and I am not an expert on Crest, but I knew them as a competitor (before PV bought them). Their version of clip limiting used a somewhat slower attack time, that actually delivered a louder signal, with the mostly inaudible leading edge or complete very brief transients passing unmolested and allowed to clip. In my experience consumers always liked louder better, so the Crest variant was successful in the marketplace while not preventing as much clipping as other more conservative clip limiters. Worst clip limiter I ever heard was one Yamaha amp model (no I don't recall which one) we were bench testing, but I wouldn't expect all of them to sound that bad (they couldn't). When operating at the limits of amplifier current capability (2 ohm) this is not very surprising. Add the variables of loudspeakers that are not pure resistive loads, and some amps with VI (secondary breakdown) limiting protection. This secondary breakdown protection is a variant on current limiting that involves both current and voltage across the power device, so different than simple current limiting. Audible perturbations could occur related to protection circuits tripping when driven hard with marginal loads. Not to mention different duty cycle capability. This may not show up with resistive loads. This is yet another reason I don't advocate routine 2 ohm operation... Spec your system to work well within the capability of the amps (4-8 ohm) and use the extra drive capability to use in emergencies if an amp failure occurs so you can double up a load to finish the gig. If all amps are loaded to the max you have no option to limp along. (Back in the day I've heard anecdotes of finishing shows loaded to 1 ohm but it wasn't pretty.) Customers are attracted to driving amps at 2 ohms since it seems like free power. Nothing in life is free... That said I expect the modern generation class D amps to be somewhat less affected by load impedance (ignoring frequency response interaction with output filters). It is difficult to make listening evaluations of amps driving loudspeakers. One test we tried at Peavey during development of one amp series, was to load up an amp with some PA speakers, in parallel with a second pair of low efficiency studio monitors in a different isolated sound space, so we could drive the amps hard but listen over the studio monitors without hurting ourselves (I still wore plugs). We kind of explored this duty cycle issue (or at least I raised it) back when Bink did his amp shoot-out years ago. JR [/QUOTE]
Insert quotes…
Verification
Post reply
Home
Forums
Pro Audio
Varsity
Suspect amp power ratings
Top
Bottom
Sign-up
or
log in
to join the discussion today!
